This invention relates to novel anaerobic curing compositions containing conventional polymerizable (meth)acrylate monomers, a free radical initiator, and a novel reactive thickener. It also relates to a process for preparing the thickener. It further relates to the use of the improved anaerobic compositions as adhesives and sealants.
Anaerobic compositions are well-known in the art. They are so formulated or treated that the compositions remains in an uncured state over long periods of time provided that the compositions are exposed to an adequate supply of air or oxygen throughout that period, but which polymerize spontaneously upon the exclusion of air or oxygen therefrom, as when placed between non-porous surfaces (e.g. metal or glass). Depending upon the exact formulation, such compositions may be used as adhesives or sealants.
It is known to incorporate as thickeners in anaerobic compositions inorganic compounds such as Cabosil (trade name for a fumed silica supplied by the Cabot Corp.), tackifiers such as rosins, rosin derivatives and terpenes, polymeric thickeners such as methacrylate and styrene-methacrylate polymers, and synthetic rubbers such as butadiene-styrene and butadiene-acrylonitrile. These thickeners do little to improve the final properties of the cured compositions since they do not take part in the final cure but remain as a separate component in the cured adhesive or sealant.
The object of this invention is to prepare novel and improved anaerobic compositions, useful as adhesives and sealants, which have incorporated therein, as a novel reactive thickener, a polymerizable polymeric adduct having pendant double bonds which is dissolved in a polymerizable monomeric diluent. It is a further object to prepare the thickener by reacting a polymer containing reactive anhydride groups with an excess of a hydroxy-containing (meth)acrylate monomer.